Using differents API in a program

What do you think about using different API in a program?
I was wondering about because I´m learning Windows programming, and I used others libraries like SDL. I think thats it is OK if none of the used API mess with another, but I´m talking about good programming pratics. Sorry for the bad english...
Is it correct?

There shouldn't be any conflicts as far as the code is concerned. It is common to use different APIs which do different things in the program.

I'd be cautious about using different APIs which do the same thing in a program though. You don't, for example, really want two different APIs trying to draw on the screen at the same time. It would be a real pain to maintain later if they overlap like that. Anyways, thats just my opinion.

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